The degree of phosphorus saturation (DPS) represents the ratio of sorbed phosphorus (P) to the P sorption capacity (PSC) of soils. In some countries, DPS is used to evaluate the risk of P loss and surface ... [more ▼]

The degree of phosphorus saturation (DPS) represents the ratio of sorbed phosphorus (P) to the P sorption capacity (PSC) of soils. In some countries, DPS is used to evaluate the risk of P loss and surface water eutrophication. This study investigated DPS measurement and prediction in neutral loamy soils fromWallonia, Belgium. A total of 57 agricultural topsoil samples subject to diverse P management were evaluated. No satisfactory relationship could be found between PSC determined by a one-point short-term isotherm in the laboratory and the sum of aluminium and iron extracted by oxalate (Alox +Feox). The equation PSC=a Alox +b pHw appeared to be more appropriate for estimating PSC in the soils studied. These soils had a near-neutral pH, and P fixation processes linked to the presence of calcium ions or carbonates were important. Comparisons of DPS with soil-test P and water-extracted P suggested that DPS could be a useful agronomic and/or environmental indicator. Our results also showed that DPS values between 20 and 30% corresponded to the agronomic optimum of soil P content. Consequently, DPS may be used as an indicator of P status in neutral soils, provided that the PSC assessment is adapted to the local soil characteristics. [less ▲]

Four water catchments used by the Walloon Society of Water (SWDE) in the rural village of Arquennes (Province of Hainaut, Belgium) have been contaminated by nitrate (concentrations between 60 and 70 mg ... [more ▼]

Four water catchments used by the Walloon Society of Water (SWDE) in the rural village of Arquennes (Province of Hainaut, Belgium) have been contaminated by nitrate (concentrations between 60 and 70 mg NO3-·l-1) for several years. The catchment basins (31 ha and 47 ha) are located exclusively in a cultivated area on loamy soils. Since October 2004, these basins have been used as a pilot area for the environmental evaluation of good agricultural practices as regards nitrogen management (adaptation of amounts of mineral nitrogen fertilizers, farm manure management, soil cover after harvest, etc.) thanks to monitoring by farmers. This approach fits into the general pattern of the Sustainable Nitrogen Management Program (PGDA in French), which implements the European Nitrates Directive as part of Walloon legislation. The second objective of the working scheme is to study and to set up a decision-making tool aimed at preventing the contamination of water by agricultural nitrate around water catchments. Two numerical models (SWAT and FEFLOW®) were used together in order to simulate the passage of water and nitrogen from the soil surface to the water catchments outlets. Calibration and validation of models were based, among other things, on soil and subsoil characterization and on tracer testing in both saturated and unsaturated zones. Moreover crop yield, farming practices, water and nitrate fluxes in water catchments, groundwater levels and nitrate concentration in groundwater were monitored for eight years. The results of simulations show that the application of PGDA in Arquennes watersheds would lead to a decrease in nitrate concentration (to almost 50 mg NO3-·l-1) in water catchments in 2012. This expected improvement in water quality has been visible since 2009 in water catchments, with mean nitrate concentrations of lower than 50 mg NO3-·l-1 at the end of 2012. [less ▲]

Under the four-year review of the program of action for the implementation of the Nitrates Directive in the Walloon region, a workshop was held a couple of scientists to assess the current program and to ... [more ▼]

Under the four-year review of the program of action for the implementation of the Nitrates Directive in the Walloon region, a workshop was held a couple of scientists to assess the current program and to propose ways of improvement [less ▲]

Since 2003, nitrate leaching has been monitored in six plots located in a loamy area (Hesbaye, Belgium), mainly dedicated to wheat, sugarbeet and vegetable crops. Open-field lysimeters have been used in ... [more ▼]

Since 2003, nitrate leaching has been monitored in six plots located in a loamy area (Hesbaye, Belgium), mainly dedicated to wheat, sugarbeet and vegetable crops. Open-field lysimeters have been used in order not to impede agricultural operations. Lysimeters are used as follow-up tools to quantify the amounts of nitrate leaching below the root zone. This study aims to evaluate the suitability of PLN (Potentially Leachable Nitrogen – APL in French) defined in the Sustainable Nitrogen Management Program (PGDA in French) as an environmental indicator by relating nitrogen management practices (including fertilization recommendations) to PLN values and groundwater quality. This study demonstrates that lysimeters are efficient in collecting representative amounts of leaching water. Lysimeters show that PLN is identified as being related to the nitrate content in leaching water, which will not be taken up by the next crop. The amount of nitrate leaching below the root zone demonstrates the necessity and the relevance of the organic nitrogen spreading limits defined in the Sustainable Nitrogen Management Program. The lysimeter tool also shows that respect for leaching water quality standards under agricultural plots needs to be considered from an integrated and generalized approach, taking into account complete crop sequences and rotations, including rational fertilization rates and the introduction of catch crops in rotation. Some suitable or unsuitable crop sequences with regard to good groundwater quality are listed. [less ▲]

Based on observations in the field, for ten years, Gembloux Agro-Bio Tech (ULg) and the Catholic University of Louvain set annual benchmarks for nitrate-nitrogen concentrations in the soil at the ... [more ▼]

Based on observations in the field, for ten years, Gembloux Agro-Bio Tech (ULg) and the Catholic University of Louvain set annual benchmarks for nitrate-nitrogen concentrations in the soil at the beginning of the leaching period (referred to as ‘PLN’ - Potentially Leachable Nitrogen). These values are used as a reference to monitor farmers located in vulnerable zones, with the monitoring being carried out by the Public Service of Wallonia. Soil samples were taken twice a year (October and December) from approximately 250 plots subjected to reasoned nitrogen fertilization. The plots were located within 34 reference farms (constituting the Agricultural Survey Areas). The samples were then analyzed for nitrate-nitrogen content. The results allowed to establish reference values for eight classes of cultivation or meadow. Analysis of the results recorded in 2011, as in previous years, illustrates the importance of “crop” and “year” in establishing reference values. [less ▲]

In accordance with the Nitrates Directive, the third “Durable Nitrogen Management Plan” (PGDA) will be soon reviewed in Wallonia (Belgium). The second “Nitrate – Water” workshop took place between 28th ... [more ▼]

In accordance with the Nitrates Directive, the third “Durable Nitrogen Management Plan” (PGDA) will be soon reviewed in Wallonia (Belgium). The second “Nitrate – Water” workshop took place between 28th May and 1st June 2012. The workshop was attended by both Belgian scientists (Université catholique de Louvain - UCL, Walloon Agricultural Research Center CRA-W, Université de Liège - ULg, Gembloux Agro-Bio Tech) and French scientists (National Institute for Agricultural Research - INRA). In the light of the results of experiments presented by scientists at this workshop, modifications to the PGDA are now recommended. These concern organic and mineral nitrogen fertilization for crops and meadows; catch crops; soil nitrate-nitrogen residue limitation in autumn, at the start of the nitrate leaching period; the management of meadow ploughing and a modification of the dairy cow standard for nitrogen production. [less ▲]

In accordance with the Nitrates Directive, the third "Durable Nitrogen Management Plan" (PGDA) will be soon reviewed in Wallonia (Belgium). The second "Nitrate - Water" workshop took place between 28th ... [more ▼]

In accordance with the Nitrates Directive, the third "Durable Nitrogen Management Plan" (PGDA) will be soon reviewed in Wallonia (Belgium). The second "Nitrate - Water" workshop took place between 28th May and 1st June 2012. The workshop was attended by both Belgian scientists (Université catholique de Louvain - UCL, Walloon Agricultural Research Center CRA-W, Université de Liège - ULg, Gembloux Agro-Bio Tech) and French scientists (National Institute for Agricultural Research - INRA). In the light of the results of experiments presented by scientists at this workshop, modifications to the PGDA are now recommended. These concern organic and mineral nitrogen fertilization for crops and meadows; catch crops; soil nitrate-nitrogen residue limitation in autumn, at the start of the nitrate leaching period; the management of meadow ploughing and a modification of the dairy cow standard for nitrogen production. [less ▲]

Within the Walloon Action Programme, transposition of the Nitrates Directive, the Administration organizes each year a control of the soil nitrate nitrogen residues in about 900 parcels located in ... [more ▼]

Within the Walloon Action Programme, transposition of the Nitrates Directive, the Administration organizes each year a control of the soil nitrate nitrogen residues in about 900 parcels located in vulnerable zone in order to verify if the practices of nitrogen spreading by the farmers are in accordance with the Walloon Action Programme. The current method is to yearly spot “suspects” by a control in three parcels in about 300 farms and to follow “suspects” by an observation programme wich leads after maximum six years to a penalty or to the end of this programme. The present statistical study means to assess the public control’s methodology: what is the probability to penalize a “good” farmer, to forget a “bad” farmer? This study is based on real data and on a theoretical approach. Both conclusions indicate that the official methodology is sufficiently appropriate. [less ▲]

in Fraters, Dico; Kovar, Karel (Eds.) Developments in monitoring the effectiveness of the EU Nitrates Directive Action Programmes. Results of th second International Workshop, 10-11 june 2009 (2011, June)

Wallonia (Southern Region of Belgium) has implemented the Nitrates Directive by designating four vulnerable zones (now 42% of the territory) and introducing a first Action programme at the start of ... [more ▼]

Wallonia (Southern Region of Belgium) has implemented the Nitrates Directive by designating four vulnerable zones (now 42% of the territory) and introducing a first Action programme at the start of November 2002 and a second one in 2007. The Action programmes entail various means of reducing the risks of the pollution of water by nitrate: (a) struggle against nitrate losses in fields using a range of good agricultural practices, including certain restrictions on the use of fertilisers (quantities, spreading periods, soil conditions, etc.), (b) keeping a balance on each farm between the organic nitrogen produced and spreading capacities on agricultural land, (c) adapting storehouses for livestock effluent to a capacity of 6 months and (d) promoting transfers of livestock effluent between farms in excess balance and farms which still have a way of using it on their land. The paper presents the principle of “soil nitrate residue” measurements (APL in French) that permits a yearly monitoring of the farming practices and constitutes a self-evaluation tool for the farmers. The paper also introduces the reference model EPICgrid dedicated to nitrogen transfer modelling in the context of the Walloon region. Following the first comparison exercise, these tools are consistent and complementary approaches to help farmers and authorities in nitrogen management. In the context of the Walloon region, dealing with deep groundwater bodies, fast indicators of potentially leachable nitrogen and nutrient fate modelling are the most practical way of assessing effectiveness of the EU nitrate directive action programmes. [less ▲]

in IWA. World Water Congress and Exhibition. Proceedings (2010, September)

The European Nitrate Directive (91/676/CEE) aims at moderating or preventing water pollution from nitrates released by agricultural practices. The Belgian Walloon region transposed it into law and ... [more ▼]

The European Nitrate Directive (91/676/CEE) aims at moderating or preventing water pollution from nitrates released by agricultural practices. The Belgian Walloon region transposed it into law and initiated a Sustainable Nitrogen Management Program in 2002 (also called PGDA in French). The non-profit association NITRAWAL amongst others, is in charge of providing support to farmers to implement and respect this program. GRENeRA is one of the organizations designated for scientific studies. In this frame, GRENeRA and its partners implemented six lysimeters in agricultural open fields, operated under real conditions of industrial harvest crops, especially vegetables. The lysimeters are used as follow up tools to monitor and quantify the amount of nitrates leaching beyond the root zone towards underground water reserves. This study demonstrates that lysimeters are efficient and permit the collection of representative samples of seepage water. On a quality stand point, nitrate content combined with data related to agricultural practices, fertilisation rates applied and advised, climate, the defined environmental indicator (APL) provide a global approach to link agricultural practices and underground water protection from nitrate pollution. The lysimeters validate the reliability of the environmental indicator (APL) with the nitrate content in leaching water, which will not be uptaken by the next crop. Unfortunately, it is also demonstrated that even when the nitrogen management is respectful of the current legislation, the goal to comply with the targeted standards of water quality is not ensured. The lysimeter tool clearly show that the respect of seepage water quality standards issued from industrial agriculture does not have to be considered per crop but rather from an integrated and global perspective of the complete crop sequence and rotations, in respect with best agricultural practices, reasonable fertilisation rates, inset crops, etc., for each individual crop being part of the overall rotation. Some favourable and non favourable crop sequences with respect to nitrates content of underground water are summarized. Experiments are in progress on crop sequence evaluation and fertilisation levels and recommendations for Belgian Walloon industrial crops and their associated impacts on the leaching water quality and nitrate content collected by lysimeters. [less ▲]